<!DOCTYPE html>
<html lang="ch">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
  </head>
  <body>
    <script>
      //   alert("hello, js");
      var a = 123;
      window.alert(a);

      window.alert("这是window.alert");
      document.write("这是document.write");
      console.log("这是console.log");
    </script>
    <!-- <script src="jsdemo.js"></script> -->
  </body>
</html>
